1. Field of the Invention
This invention relates to fire hydrants and more particularly to fire hydrants that discourage unauthorized use.
2. Description of the Related Art
Fire hydrants are installed in water systems to provide water at the pressures and flow rates needed for fire fighting, but when hydrants are opened illicitly, say for recreational purposes during the heat of summer, not only does the resulting flow flood streets, undermine infrastructure and put the lives of children at risk; it also reduces pressures and flow rates to levels too low for effective fire fighting.
Fire hydrants intended to discourage this unauthorized use are familiar from the patent literature, and examples include Barton, U.S. Pat. No. 5,520,210; Camp, U.S. Pat. No. 4,716,922; Etter et al., U.S. Pat. No. 5,622,202; Meneses, U.S. Pat. No. 5,588,460; Pollard, U.S. Pat. No. 5,469,724; Sigelakis, U.S. Pat. No. 5,549,133; Stehling et al., U.S. Pat. No. 5,596,893, and Sutton, U.S. Pat. No. 3,650,471.
Barton and Meneses teach hydrants that are intended to be operated only with special mechanical wrenches, but such hydrants have also been opened with improvised versions of these wrenches. Camp and Stehling teach hydrants that are intended to be operated only with special magnetic wrenches, but such hydrants have also been opened with the combination of loudspeaker magnets and conventional wrenches. Pollard and Sigelakis teach external hydrant locking devices intended to deny illicit access to water, but these devices have been smashed to gain access to that water. Etter teaches a hydrant that is opened or closed by pumping fluid from an external source to a turbine inside the hydrant, and Sutton teaches an arrangement having an auxiliary valve that provides a recreational spray even with the main valve closed. Sutton does not, however, include means for limiting the flow to only that spray during unauthorized use.
Other relevant literature includes the American Water Works Association (AWWA) publications AWWA Standard for Dry Barrel Fire Hydrants, ANSI/AWWA C502-85, Denver, 1985, .sctn.3.2.1, 3.2.1.2, 3.2.11 and 3.2.9.1 in particular; AWWA Standard for Wet Barrel Fire Hydrants, ANSI/AWWA C503-82, Denver, 1982; and Installation, Field Testing, and Maintenance of Fire Hydrants, AWWA Manual M17, Third Edition, Denver, 1989. Pages 94 and 95 of Manual M17 show the internal details of U.S. Pipe & Foundry Co. Series H Hydrant with Pilot Valve for Higher Pressures, an arrangement of particular relevance here.